As the glaciers passed through here 10,000 years ago, they did us some great favours. For one, the Great Lakes were carved out of the hard earth providing us with an abundant source of fresh water that should last forever, if we don’t botch it up. They also left us with superior soil in the southwestern part of the province that is, for the most part, rock free and of such a fine, sandy/loamy till that soil lovers anywhere would fall to their knees, scoop it up in their hands and breathe deeply the wonders of life that thrive within.

Alas, here in the GTA, most of us are blessed with clay-based soil that is great for pottery and bricks, but when it comes to growing a great garden all we can really do is try our best to change the quality of the clay and to live with it. Once again, I am here to help.

If you happen to live in the clay belt, there is some good news. First of all it helps to understand why clay-based soil is tough on most plants. The soil particles of clay are very small and they stick together like glue. When clay is wet it sticks to your boots, when it is dry it sticks together (notwithstanding the large cracks that occur in it during a drought).

Breaking up clay particles is no small matter. I have done battle with the stuff in my own gardens and I find one of the best amendments is good old-fashioned sand. Look for builder’s sand or play sand (for the sand box, not beach sand). Coarse builder’s sand will open up the pores of the clay providing much needed space for oxygen and water to flow through. It is, after all, the lack of oxygen that makes it difficult for so many plants (but not all) to thrive in clay, and it is the abundance of water that causes roots to rot.

Add To Clay

Another useful amendment to clay soil is gypsum. There is a chemical relationship between clay particles and gypsum that creates a much more desirable environment for plants to grow. Take my word for it. Spread some gypsum on the lawn by the road and it will change its behaviour. In time (three to four months perhaps) the soil will open up and allow new lawn roots to develop below the surface of the soil. Voila, a better looking lawn.

Plant High

Mound good quality soil up to your plants rather than planting them deeply in the ground. Digging a hole for a plant in clay is not much different than planting in a bowl. Great for holding your cereal and milk but not so good for root development. Planting on a berm or raised garden also works. Just be sure to use good soil in the first place.

Encourage Drainage

By trenching, or installing drainage pipes, you can help to move water from soggy, clay areas. However, you will still need to improve the quality of the soil.

Clay Tolerant Plants

There are a lot of plants that tolerate clay soil. Few actually thrive in it, but as always it is best to take our cue from Mother Nature. Check out my list of clay tolerant plants below and note that there are other tactics that you can employ to ensure the greatest possible success in your clay-belt garden.

Trees

• Silver maple (Acer Saccharinum): Grows quickly and does not know when to stop.

• River birch (Betula Nigra): A fine ornamental tree with bark that will eventually turn white.

• Hackberry (Celtis): A native tree that grows slowly but is worth the wait.

• Common honeylocust (Gleditsia): The “Black Locust” is a bit dirty as it drops branches and seed pods at the end of the season, but it makes up for it with its naturally high reaching branches.

• European larch (Larix deciua): A deciduous evergreen that grows quickly. I like the look of a grove of larch.

• Bur oak (Quercus macrocarpa): Another slow growing native but with luck your grandchildren will sling a hammock in it. Tall and rather narrow growth habit.

• White cedar (Thuja occidentalis): Yes, the same evergreens that we use to plant permanent hedges. Versatile, fast growing and a nice specimen as a tree or as a hedge (with annual trimming of course).

Flowering Shrubs

• Serviceberry (Amelanchier): A native shrub that is first to bloom in spring. Attracts birds to its fruit later in summer and early fall.

• Quince (Chaenomeles): Fruiting quince have attractive flowers in early May and the fruit, which is much like an apple in appearance, is a great freshener for your fridge. Cut it in half and use it instead of baking soda.

• Cotoneaster (Acutifolia): I don’t know why we don’t plant more Peking cotoneaster. It is entirely winter hardy, features attractive glossy green leaves, white spring flowers and fruit that cardinals and cedar waxwings enjoy. Grows to about four meters unless you trim it down.

• Forsythia: The yellow, early spring flowering shrub that we are all familiar with.

• Canadian holly (Mahonia): A deciduous evergreen, it drops its leaves in the spring as new growth develops; fascinating. Birds enjoy the fruit, clusters of yellow flowers in June.

• Highbush cranberry (Viburunum opulus): A native that flowers nicely in May, produces an abundance of attractive berries that birds like come March, after hanging there all winter.

• Bee balm (Monarda): A native that loves the sun and attracts hummingbirds.

• Rodgersia: An easy to grow broad-leafed perennial that looks as good out of flower as it does when in bloom.

Planting in clay is not a lost cause; it just demands that you follow the yellow brick road to a great looking garden. Or you can dig all of the clay out and start again with quality triple mix. As I say, if you need a pickaxe to dig it, you probably should remove it.

Question of the Week

Q: I have many iris plants and this year there are many fronds, but few flowers. How can I get them to produce more flowers?

• Lack of moisture: irises may not bloom if they experience a dry period during flower bud production.

• Overcrowding: overcrowded clumps stop blooming until they are divided.

Mark Cullen is an expert gardener, author and broadcaster. You can sign up for his free monthly newsletter at markcullen.com, and watch him on CTV Canada AM every Wednesday at 8:45 a.m. You can reach Mark through the “contact” button on his website and follow him on Twitter @MarkCullen4 and Facebook. Mark’s latest book, Canadian Lawn & Garden Secrets, is available at Home Hardware and all major bookstores.

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